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Appl Environ Microbiol, July 1998, p. 2443-2448, Vol. 64, No. 7
Department of Microbiology, University of
Barcelona, Barcelona 08028, Spain
Received 22 December 1997/Accepted 28 April 1998
Shiga toxin-converting bacteriophages are involved in the
pathogenicity of some enteric bacteria, such as Escherichia
coli O157:H7, but data on the occurrence and distribution of such
phages as free particles in nature were not available. An experimental approach has been developed to detect the presence of the Shiga toxin 2 (Stx 2)-encoding bacteriophages in sewage. The Stx 2 gene was amplified
by PCR from phages concentrated from 10-ml samples of sewage. Moreover,
the phages carrying the Stx 2 gene were detected in supernatants from
bacteriophage enrichment cultures by using an Stx 2-negative E. coli O157:H7 strain infected with phages purified from volumes of
sewage as small as 0.02 ml. Additionally, the A subunit of Stx 2 was
detected in the supernatants of the bacteriophage enrichment cultures,
which also showed cytotoxic activity for Vero cells. By enrichment of
phages concentrated from different volumes of sewage and applying the
most-probable-number technique, it was estimated that the number of
phages infectious for E. coli O157:H7 and carrying the Stx
2 gene was in the range of 1 to 10 per ml of sewage from two different
origins. These values were approximately 1% of all phages infecting
E. coli O157:H7.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Abundance in Sewage of Bacteriophages That Infect
Escherichia coli O157:H7 and That Carry the Shiga Toxin
2 Gene
*
Corresponding author. Mailing address: Department of
Microbiology, University of Barcelona, Avenida Diagonal 645, Barcelona 08028, Spain. Phone: 34 3 402 14 87. Fax: 34 3 411 0592. E-mail: joan{at}bio.ub.es.
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